48 lines
998 B
C
48 lines
998 B
C
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/* Delay and force.
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*/
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#include "kernel.h"
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Object P_Promisep (x) Object x; {
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return TYPE(x) == T_Promise ? True : False;
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}
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Object P_Delay (argl) Object argl; {
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Object d;
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GC_Node;
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GC_Link (argl);
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d = Alloc_Object (sizeof (struct S_Promise), T_Promise, 0);
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GC_Unlink;
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PROMISE(d)->done = 0;
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PROMISE(d)->env = The_Environment;
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PROMISE(d)->thunk = Car (argl);
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return d;
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}
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Object P_Force (d) Object d; {
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Object ret, a[2];
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GC_Node;
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TC_Prolog;
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Check_Type (d, T_Promise);
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if (PROMISE(d)->done)
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return PROMISE(d)->thunk;
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GC_Link (d);
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a[0] = PROMISE(d)->thunk; a[1] = PROMISE(d)->env;
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TC_Disable;
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ret = P_Eval (2, a);
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TC_Enable;
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GC_Unlink;
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if (PROMISE(d)->done) /* take care of recursive force calls */
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return PROMISE(d)->thunk;
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PROMISE(d)->thunk = ret;
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PROMISE(d)->done = 1;
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return ret;
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}
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Object P_Promise_Environment (p) Object p; {
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Check_Type (p, T_Promise);
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return PROMISE(p)->env;
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}
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